Placement of a catheter into a blood vessel of a human patient may be performed for a variety of medical, therapeutic and diagnostic purposes. For example, percutaneous insertion of a catheter into the jugular or subclavian vein is often performed to enable measurement of central venous pressure or to facilitate total intravenous feeding or to administer other intravenous therapy.
Percutaneous insertion of a catheter (herein “catheterization”) into a blood vessel generally involves the use of a catheter-over-needle or a catheter-through-catheter placement technique. The catheter-over-needle placement technique generally uses a catheter of up to about four inches in length that has a tapered end with a sharp, straight needle or stylet extending from the tapered end. The needle or stylet is inserted into a blood vessel, after which the needle or stylet is withdrawn. The catheter may then be pushed further along the blood vessel.
Difficulties in catheterizing certain kinds of patient may arise using a catheter-over-needle technique. Elderly patients or drug-abusers may have veins that are particularly susceptible to needle damage, either from fragility or prior abuse. Also, in obese patients the correct depth of needle or stylet insertion may be difficult to assess, resulting in an increased probability that the blood vessel may be missed or penetrated completely resulting in vessel damage and bleeding into the surrounding tissues.
Difficulties in catheterization using prior art devices may also arise where direct access to a target blood vessel is blocked by bone or other obstruction as may occur, for example, in catheterization of a subclavian vein.
Catheterization of blood vessels oriented substantially parallel to the skin can be problematic because insertion of the needle or stylet at a large acute angle relative to the skin results in penetration of the blood vessel wall at a corresponding large acute angle and increased probability of damage or penetration of the opposite blood vessel wall. While this problem may be somewhat ameliorated by inserting the needle or stylet into the skin at a small acute angle, this technique either increases the length of the catheterization device required or reduces the length of the catheter that is available for insertion into the blood vessel.
Further, the catheter-over-needle technique requires that the needle or stylet and the overlaying catheter must be handled carefully during catheterization to minimize the risk of damage to the wall of the catheter. Thus, for example, flexing of the stylet should be avoided.
While elaborate devices and techniques are known for the guidance of catheters once inserted into a blood vessel (see, e.g., U.S. Pat. Nos. 4,468,224, and 6,379,346 B1), and for the production of catheters capable of assuming a desired shape once the needle or stylet is withdrawn (see, e.g., U.S. Pat. Nos. 3,719,737 and 5,044,369), these approaches do not address the difficulties described above relating to initial catheterization.
Therefore, notwithstanding the existence of a variety of catheterization devices in the prior art, there is a continuing need for a device that permits catheterization of veins for which a direct approach is blocked by bone or other obstruction, and for a device that lessens the risk of vein wall damage in catheterization of blood vessels of drug abusers, the obese, and the elderly, and the present invention substantially fulfills these needs. All this and more will become apparent to one of ordinary skill, upon reading the disclosure, drawings, and claims appended hereto.